Microlithography is used in the fabrication of microstructured components like integrated circuits, LCD's and other microstructured devices. The microlithographic process is performed in a so-called microlithographic exposure system including an illumination system and a projection lens. The image of a mask (or reticle) being illuminated by the illumination system is projected, through the projection lens, onto a resist-covered substrate, typically a silicon wafer bearing one or more light-sensitive layers and being provided in the image plane of the projection lens, in order to transfer the circuit pattern onto the light-sensitive layers on the wafer.
In order to obtain a good interference contrast of the image created in the image plane of the projection lens, it can be advantageous to have a two-beam-interference of light rays each being polarized perpendicular to the plane of incidence. It can be desirable to have a so-called tangential polarization distribution, where the planes of oscillation of the electrical field vectors of individual linearly polarized light rays in a pupil plane of the system have an orientation that is perpendicular to the radius originating from the optical axis.